In the processing of a semiconductor wafer to form integrated circuits, a number of traces are normally formed over an underlying layer. The traces are normally used to interconnect transistors and other devices in the integrated circuits. Such traces may have widths under 0.2 micrometers (microns), pitches (center to center spacing) under 0.4 microns and aspect ratios exceeding 4:1.
Depending on the stage of the processing, it may be necessary to measure properties of various portions of a wafer, such as the properties of the traces and/or the properties of the underlying layer. However, the presence of traces can interfere with conventional measurements that examine open areas (areas not covered by traces).